A major earthquake jolted the California-Mexico border area of the Imperial Valley today, damaging buildings, knocking out water systems and tearing up highways. At least 70 persons were hurt.

The temblor, which measured 6.4 on the richter scale, was felt as far away as Los Angeles, 200 miles to the northwest, and Las Vegas, more than 200 miles north, although no damage was reported there.

Seismologists at the California Institute of Technology said the quake was centered about 10 miles east of Calexico and up to five miles south of the Mexican border on the Imperial fault. The main shock occured at 4:16 p.m. (PDT) and was followed by at least 15 aftershocks ranging from 3.5 to 5 on the Richter scale.

At least 60 persons were being treated at hospitals but the extent of their injuries was not known.

In El Centro, about 100 miles east of San Diego, part of a six-story county services building was tilted and officials were concerned it would collapse.

Roofs collapsed on a store and a hotel in Calexico, southeast on the Mexico border.

In the neighboring Meldland area, a wall fell in at a grocery store.The owner, Mary Magallanez, said the quake "just kept rolling" and tore up nearby roadway.

In Palm Springs, less than 100 miles northwest of the epicenter, the temblor rattled windows and ruptured swimming pools.

In San Diego, Richard Berry, chairman of the geological sciences department at San Diego State University, said he became aware of the quake when his chair began moving across the room.

He said he rushed to his seismograph and watched the needle swing back and forth out of control.

"It just totally swamped our instruments," he said. "It's the biggest I've ever seen on our instruments."

At the El Centro Border Patrol headquarters, Deputy Patrol Chief Bill King ordered the building evacuated for more than 15 minutes after the main shock.

"It was pretty frightening, and I guess it lasted between 30 seconds and a minute," he said.

In Mexicali, the capital of Baja California, an official government spokesman said the temblor was very strong but that he had no reports of extensive damage. One death was reported in Mexicali.

The All American Canal, which parallels the border in Imperial County, was damaged "extensively" 15 miles east of El Centro, according to deputy sheriffs.